Repairing aluminum-PEEK hybrid metal-polymer joints made by thermo-mechanical joining

Hybrid multi-material joints are demanded in several fields, including automotive, aerospace, defense, and biomedical. The repairing process of hybrid multi-material joints made of metal and polymer using friction -assisted joining is investigated. The experimental test campaign was conducted by joining aluminum alloy AA7075 and Polyether-ether-ketone (PEEK). The aluminum surface was previously texturized using different laser texturing strategies. After joint failure, the two substrates were repaired using friction-assisted joining and subsequently mechanically tested. Fracture surface and cross-sectional analysis were performed using optical and scanning electron microscopy. Two main failure mechanisms were identified, namely aluminum teeth fracture and pull-out. After repair, the joints that failed by aluminum teeth fracture showed lower mechanical behavior. Conversely, the joints that failed by pull-out showed even higher mechanical behavior after repair. The adoption of dense texturing strategies (hatch distance of 0.2 mm) increased the peak force by 17 % and the absorbed energy by 32 % after repairing. This indicates that the selection of proper laser texturing conditions can also be aimed at improving the joint's properties after repair.